This invention relates to packet routing in a packet routing or exchange network in which a plurality of routers, with each router connected to a plurality of local area networks (LAN's), are connected to one another through a public network. More particularly, this invention relates to a packet routing method, to a packet routing network, and to a router for use in the packet routing network. Such a router is often called a remote router in the art.
The local area networks comprise terminal equipments for use by subscribers in transmitting and receiving data as data packets. When intentionally used by the subscribers, the data packets will be called subscriber packets. In order to charge individual subscribers for or in connection with the subscriber packets, charging apparatus is used either in each local area network or in each router. It is herein intended that inclusion of the public network in the packet routing network means use of the charging apparatus between each pair of local area networks used in the packet routing network.
For transmission and reception of the data packets, it has been a preferred practice in each router to resort to dynamic routing by using a routing information protocol (RIP) as a routing protocal indicative of routing or connection information among the local area networks of the packet routing network. In general, each router comprises a routing table. On describing the dynamic routing a little more in detail, attention will be directed to an arbitrary pair of the routers. One of the pair will be called a local router. The other will be referred to as a different router.
Subjecting to protocol processing the, routing information stored in the routing table, the local router periodically (usually, once in thirty seconds) broadcasts to other routers a routing information protocol packet as a routing information protocol datum. Such a routing information protocol datum indicates the connection information to the local area networks connected to the router under consideration. Related to the local router in this manner, the routing information protocol datum is herein called a local routing information protocol datum.
Receiving the local routing information protocol packet as an incoming or received routing information protocol datum, the different router stores the connection information of the incoming routing information protocol datum in its routing table as the routing information and determines an optimum path based on the routing information between a pair of local area networks. One of this pair is connected to the local router. The other is connected to the different router. Consequently, the routing information is in general for use in determining the optimum path, which is similar to the best path as called by Leonard Bosack in U.S. Pat. No. 5,088,032.
In a conventional packet routing network including a public network, only the subscriber packets are delivered to the public network. The routing information protocol packets and like packets should not be delivered to the public network. This is in consideration of use of the charging apparatus and has made it inevitable to use static routing in each router. When the static routing is resorted to, each router preliminarily stores the routing information in its routing table. Based on this preliminarily stored information, the router controls routing of the data packets to the local area networks connected to the router in question.
In such a conventional router, it is impossible for each router to dynamically get the routing information. It has therefore been unavoidable, when current routing information is changed in one of the routers to new routing information, to somehow inform other routers of this change and to manually update the current routing information to the new routing information in their routing tables.